Field of the Invention
The present invention relates to the field of Web services and more particularly to policy processing in a policy document.
Description of the Related Art
The achievement of universal interoperability between applications by using Web standards remains the principal goal of Web Services. Web Services use a loosely coupled integration model to allow flexible integration of heterogeneous systems in a variety of domains including business-to-consumer, business-to-business and enterprise application integration. The following basic specifications originally defined the Web Services space: the Simple Object Access Protocol (SOAP), the Web Services Description Language (WSDL), and Universal Description, Discovery, and Integration (UDDI). SOAP defines an XML messaging protocol for basic service interoperability. WSDL introduces a common grammar for describing services. UDDI provides the infrastructure required to publish and discover services in a systematic way. Together, these specifications allow applications to find each other and interact following a loosely coupled, platform-independent model.
Presently, the interaction model that is directly supported by WSDL essentially can be viewed as a stateless model of synchronous or uncorrelated asynchronous interactions. Models for business interactions typically assume sequences of peer-to-peer message exchanges, both synchronous and asynchronous, within stateful, long-running interactions involving two or more parties. Nevertheless, systems integration requires more than the mere ability to conduct simple interactions by using standard protocols. The full potential of Web Services as an integration platform will be achieved only when applications and business processes are able to integrate their complex interactions by using a standard process integration model.
WS-Policy is a specification that allows Web services to use XML to advertise the message exchange policies of the Web service, such as relates to security, and Quality of Service, for Web service consumers to specify policy requirements. WS-Policy represents a set of specifications that describe the capabilities and constraints of the security (and other business) policies on intermediaries and endpoints. Examples include required security tokens, supported encryption algorithms, and privacy rules, to name a few. WS-Policy further specifies how to associate policies with services and endpoints.
A policy according to WS-Policy can be attached at different portions of the WSDL structure so that the policy domain is left to define the combining rules when different policies of the same domain appear within the same branch of a WSDL tree. Because a WSDL message part can be used in a particular message exchange—whether request or response—a policy statement inherently can be bi-directional. In particular, new messaging specifications, such as WS-Addressing, supply endpoint references to a WSDL document. The inclusion of policy statements in different endpoint references have resulted and those policy statements are inherently bi-directional. Accordingly, the management process undertaken in response to a particular policy can vary depending upon the direction of a message, e.g. whether the message is a request or a response.